The boss of AstraZeneca raised the stakes over the controversial takeover threat by US rival drugmaker Pfizer by warning on Tuesday that an aggressive cost-cutting plan by the American firm could cost the lives of cancer patients.

Pascal Soriot, AstraZeneca's chief executive, told MPs that the development of life-saving cancer drugs could be significantly delayed by the combined companies "saving tax and saving costs".

Soriot, who is desperately fighting Pfizer's plans to gobble up his company in the biggest ever foreign takeover of a British firm, said the planned £63bn deal could severely jeopardise the development of some of the world's most promising drugs.

"Any distractions on work we are doing now could run the risk of delaying our drugs pipeline," he said. "From the lab to the patient takes many years."

In an emotive appearance at the business select committee, Soriot said: "What will we tell the person whose father died from lung cancer because one of our medicines was delayed – and essentially was delayed because in the meantime our two companies were involved in saving tax and saving costs?

"It is logical to assume that a merger like this could mean substantial cost savings, and cost savings could mean job losses."

Soriot is concerned that Pfizer's proposed takeover – which the US company admitted on Tuesday would result in job cuts and a big reduction in research and development spending – could distract AstraZeneca's scientists as they approach a crucial point in the development of several potentially life-saving drugs.

Within the past week, AstraZeneca has released a string of positive test results and pushed three drugs through to late stage trials, including a lung cancer medicine fast-tracked to final stage trials.

AstraZeneca began phase III large-scale hospital trials of the cancer immunotherapy drug codenamed MEDI4736 last weekearlier successful trials at American Society of Clinical Oncology conference in Chicago later this month.

The drug, which uses the body's own defences to spot and kill cancer cells rather than attacking them with chemotherapy, is regarded as potentially one of the most groundbreaking of recent years. It could also be a big money-spinner, with AstraZeneca believes sales could peak at £3.9bn a year.

Pfizer declined to comment on the suggestion that its proposed takeover could cost lives, but its chief executive, Ian Read, told MPs that his motivation for buying AstraZeneca was to speed up the introduction of new medicines, not slow it down.

"We have an expression at Pfizer, 'Patients are waiting', and the faster we can get medicine to patients the more productive we can be and the more successful the industry will be," he said.